Ge advance scanner

Participants were not required to fast before PET scans but rather to spend the day and hours prior to scanning according to their custom. Subjects were instructed to refrain from drinking alcohol for at least 24 h before PET scanning. If applicable, participants were asked to consume caffeine and nicotine within usual limits on the day of PET scanning.
PET images were acquired on a GE Advance scanner (General Electric Medical Systems, Milwaukee, WI) with a spatial resolution of six mm full-width at half-maximum (FWHM). Emission data were acquired over 90 min after bolus-injection of 302 ± 79 MBq (mean ± SD) (+)-[¹¹C]-PHNO. Radiosynthesis was performed as described previously (Rami-Mark et al., 2013 (link), Pfaff et al., 2019 (link)). Employing filtered–back projection, images were reconstructed from sinograms to 15 one minute frames and 15 five minute frames. Attenuation correction was performed using matrices acquired immediately before tracer injection in a five minute transmission scan using a rotating ⁶⁸Ge source. All scans were corrected for decay to the time of radioligand injection. T1 and proton density (PD) weighted 3 T magnetic resonance images (MRI) were acquired for PET image co-registration and delineation of regions of interest (ROI).

Details of the PIB PET data acquisition and processing have been published previously (Annus et al., 2016 (link)). Briefly, PIB PET images were acquired in 3D mode on a GE Advance scanner (General Electric Medical Systems, Milwaukee, WI, USA) for 90 minutes post-PIB injection in 58 frames. Only participants with DS were assessed for amyloid. Cortical regional PIB analysis was based on Brodmann areas, whereas subcortical regions of interest were based on deep gray matter parcelations using FIRST (Patenaude et al., 2011 (link)) and included the striatum (caudate nucleus and putamen), amygdala, thalamus, and hippocampus. For each region of interest, nondisplaceable binding potential was obtained using a basis function implementation of the simplified reference tissue model (Gunn et al., 1997 (link)) with superior cerebellar gray matter as reference region. PIB-positive and PIB-negative groups were assigned on the basis of striatal nondisplaceable binding potential, which had previously revealed a bimodal distribution with clear separation of positive and negative groups (Annus et al., 2016 (link)). Of the 46 participants with DS, 19 were PIB-positive.